High speed digital data communications over wired or wireless communication channels are exploding in usage. Serial data communication over wires has been increasing almost exponentially in recent years. For example, traffic cameras and video on demand over internet are only two of many applications that use high speed data communications. Larger and larger amount of data is being generated, and data communication rates increase every year. It is generally desirable to store newly generated data, which typically requires sending the data from the place of generation to a different location where it will be stored. Further, once the data has been stored, means must be provided to facilitate searching and retrieval of the stored data.
Moving large amount of data usually is done with the use of Serializer-Deserializer (SERDES) transceivers. In some instances there is large attenuation between the end points where the data is to be moved. The attenuation between end points is higher at higher frequencies than at low frequencies. High speed data transfer uses large frequency bandwidth, and frequency dependent attenuation causes distortion and errors in data transmission. Today there are communication systems with SERDES devices that can transfer data at rates of more than 20 Gbps. Such large data rate communication usually requires a wide frequency bandwidth channel to carry the information, and communication channels typically have insertion losses proportional to the signal frequencies, such that higher frequency signals are attenuated more than lower frequency signals. The band-limiting due to attenuation of high frequencies in the channel cause inter-symbol interference (ISI) that ultimately results in errors. To overcome this problem it is generally necessary to equalize all frequencies in the communications bandwidth so that insertion loss is equal at all frequencies that are important in data transmission.
Another problem that equipment manufacturers face is the power dissipation because usually there are increasing number of SERDES devices in small volume that consume fairly large power. Today there are communication integrated circuits (ICs) that have 100 or more high speed SERDES transmitters and receivers. One of main problems with this kind of circuit density is that it can be difficult to remove dissipated power.
The inventors have determined a need for improved apparatus and methods for equalizing communication signals.